Atomic layer deposition is a thin film growth technique that employs a sequence of self-limiting surface reaction steps to allow sub-nanometer control of the growth process. The self-limiting adsorption reactions ensure precise control of film thickness and uniformity over large areas. For example, with ALD it is possible to ensure that growth of layer #1 is complete before growth of layer #2 on top of layer #1 is initiated. In this manner, ALD provides very accurate and precise control of device structure and composition in the growth direction (typically taken to be the z direction). However, it remains challenging to provide a comparable level of structure/composition control for ALD in the lateral directions (i.e., x and y directions).
Various methods have been investigated for providing lateral patterning capability in combination with ALD. It is important that such patterning techniques not disrupt the layer by layer growth that is characteristic of ALD, and substantial simulation and/or experimental investigation is typically required to confirm the suitability of any particular patterning methods for use with ALD. For example, one approach that has been experimentally investigated is the use of microcontact printed resists.
Another approach which has been considered for lateral patterning combined with ALD is the use of a scanning probe microscopy (SPM) tip to add or remove passivating material from a substrate surface (U.S. Pat. No. 7,326,293). The resulting pattern of passivation material controls the lateral pattern of subsequent ALD. However, this process of directly adding or removing passivation material from the surface of a substrate can be time-consuming and/or can cause difficulties in practice (e.g., when removing passivation material from a surface, the removed material may accumulate on the tip and degrade performance).
Accordingly, it would be an advance in the art to provide a tip-patterned ALD method that does not suffer from the above-identified problems.